The present invention relates to magnetic beam for a roller squeegee of a rotary screen printing installation. In particular, the present invention relates to a unique configuration in which warping of one of the key components is avoided.
One configuration for a magnetic beam includes an elongated upper plate whose longitudinal direction is perpendicular to the direction of advance of the conveyor belt, guided thereover, of the printing installation and on the underside of which a number of magnet coils, which can be energized electrically, are attached. The which upper plate is connected to a lower container which extends over virtually the entire length of the upper plate and surrounds the magnet coils and is provided with openings for natural ventilation along the magnet coils. The the magnetic beam is provided at each end with a projecting journal which rests on a member which is vertically movable and which interacts with an adjustable stop connected to the frame of the printing installation.
With magnetic beams of this type, which are generally broad and long, the problem arises that part of the energy supplied to the magnet coils is converted to heat. This heat must be removed since otherwise an impermissible rise in the temperature of the coils occurs which makes the coils less effective. This heat removal usually takes place by means of natural ventilation, which ventilation is further increased by the movement of the conveyor belt of the printing installation. The disadvantage of this natural ventilation is, however, that a temperature difference arises between the lower side and the upper side of the magnetic beam, This temperature difference results in the magnetic beam having the tendency to warp, which has an adverse effect on the operation of the printing installation.